feat: add support for server-only extractors (#5086)

examples/07-fullstack/server_functions.rs

@@ -282,7 +282,12 @@ async fn anonymous() -> Result<String> {
 /// This is less preferred over the `#[get]`/`#[post]` syntax but is still functional for backwards
 /// compatibility. Previously, only the `#[server]` attribute was available, but as of Dioxus 0.7,
 /// the `#[get]`/`#[post]` attributes are preferred for new code.
-#[server(prefix = "/api/custom", endpoint = "my_anonymous")]
+///
+/// You can also use server-only extractors here as well, provided they come after the configuration.
+#[server(prefix = "/api/custom", endpoint = "my_anonymous", headers: dioxus_fullstack::HeaderMap)]
 async fn custom_anonymous() -> Result<String> {
-    Ok("Hello from a custom anonymous server function!".to_string())
+    Ok(format!(
+        "Hello from a custom anonymous server function! -> {:#?}",
+        headers
+    ))
 }